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Three thousand years in Tibet

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National Science Review 2020年第1期7卷 129-130页

作者： Bettina Harr Trevor Price max-planck-institut für Evolutionsbiologie Department of Ecology and Evolution University of Chicago

Humans have come to inhabit nearly every terrestrial environment. Their commensals have followed them and have consequently become some of the most abundant and widespread species on Earth, in the process becoming exposed to a variety of abiotic and biotic stressors. For example, the house sparrow was introduced from the UK to North America in the

关键词： Three thousand years in Tibet

Ca-,Al-rich refractory inclusions and Pt-metal nuggets in the Ningqiang carbonaceous chondrite

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Chinese Science Bulletin 1999年第8期44卷 725-731页

作者： A.El Goresy max-planck-institut fr Kernphysik 6 900 Heidelberg 1 Germany

Petrography and mineral chemistry of Ca, Al-rich inclusions of Ningqiang carbonaceous chondrite are studied and the highly Re-Os fractionated Pt-metal nuggets in it is discovered. The refractory inclusions are classified into melilite-spinel-rich, and spinel-pyroxene-rich types. The former probably crystallized from melts, while the latter could be aggregates of the nebular condensates. The strong f ractionation between Re and Os suggests a pre-solar origin of the Pt-metal nuggets, which probably experienced various processes of formation and evolution before being captured by the refractory inclusions as indicated by the depletions of W and Mo.

关键词： meteorite refractory inclusion Pt-metal nuggets solar nebula.

Characteristics of elution profile in radial chromatography under linear conditions

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Science China Chemistry 2005年第4期48卷 352-360页

作者： Andreas Seidel-Morgenstern max-planck-institut für Dynamik Komplexer Technischer Systeme 39106MagdeburgGermany

Based on the mass balance equations of solute transfer in the radial chroma-tographic column,the theoretical expression to describe the column efficiency and shape of elu-tion profile is obtained under linear isotherm ***,the tendency for the variation of column efficiency and symmetry of peak profile is systematically *** results showed that in radial chromatography the relationship between the column efficiency and volumetric flow rate is similar with that relationship in axial chromatography;relatively high column efficiency still can be obtained under high flow rate in radial *** the increase of retention factor of solutes and injection time,the column efficiency decreases *** effect of column diameter and column length on the column efficiency interfere with each *** is more advantageous to increase the column efficiency by applying columns with larger column diameter and shorter column *** to the discussion of the effect of diffusion on the column efficiency,radial chromatography is proved to be suitable for the separation of samples with relatively high diffusion coefficient,which predicts its obvious advantage in the preparative separation of samples such as proteins and DNA.

关键词： radial chromatography, column efficiency, elution profile, symmetry.

A Note on Black Holes in Asymptotically Lifshitz Spacetime

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Communications in Theoretical Physics 2014年第8期61卷 265-271页

作者：庞大伟 max-planck-institut Für Physik (Werner-Heisenberg-institut) Fohringer Ring 6 80805 München Germany

We investigate several aspects of exact black hole solutions in asymptotically Lifshitz spacetime. Firstly,we calculate the tidal forces and find that in the near horizon region of such black hole backgrounds, the tidal forces diverge in the near extremal limit. Secondly, we evaluate the Wilson loops in both extremal and finite temperature cases. Finally, we obtain the corresponding shear viscosity and square of the sound speed and find that the ratio of shear viscosity to entropy density takes the universal value 1/4π in arbitrary dimensions while the square of the speed of sound saturates the conjectured bound 1/3 in five dimensions.

关键词： AdS/CFT correspondence AdS/CMT hydrodynamics

New insights into AGNs with low-mass black holes and high accretion rates:the case of narrow-line Seyfert 1 galaxies

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Science China(Physics,Mechanics & Astronomy) 2010年第S1期53卷 216-219页

作者： KOMOSSA S max-planck-institut für extraterrestrische Physik

Narrow-line Seyfert 1(NLS1) galaxies are believed to harbor low-mass black holes accreting at high rates,and they are therefore important targets when studying the nature of black hole growth,galaxy evolution,and accretion *** have rigorously studied the physical properties of a sample of NLS1 *** briefly review previous findings and present new results,including:(1) The locus of NLS1 galaxies on the MBH-σ plane,which we find to follow the relation of non-active galaxies after removing objects obviously dominated by outflows.(2) The presence of "blue outliers" which hint at extreme outflows as they would be predicted from merger models.(3) More subtle evidence for winds and outflows across the whole NLS1 population.(4) New correlations and trends which link black hole mass,Eddington ratio and physical parameters of the emission-line region.A new element is added to the eigenvector 1 space based on a principal component analysis,which aims at identifying the main drivers of AGN correlation properties.

关键词： active galactic nuclei emission lines density outflow

Characterization of Compositionally Complex Hydrides in a Metastable Refractory High-Entropy Alloy

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Acta Metallurgica Sinica(English Letters) 2023年第7期36卷 1173-1178页

作者： Jikui Liu Junhua Hou Fengchao An Bingnan Qian Christian H.Liebscher Wenjun Lu Department of Mechanical and Energy Engineering Southern University of Science and TechnologyShenzhen518055China max-planck-institut Für Eisenforschung Max-Planck-Straße 140237DüsseldorfGermany

Here,we study the hydride formation in a metastable Ti-33Zr-22Hf-11Ta(at.%)refractory high entropy alloy(RHEA).Deviating to non-equiatomic compositions of RHEAs promotes the formation of transformation-induced plasticity where the body-centered cubic phase transforms to hexagonal close-packed(HCP)*** is found that the phase transformation capability assists the hydride formation due to the low solubility of hydrogen within the HCP *** this study,hydrogen is charged via electrochemical polishing and the corresponding phase transformation is activated in the metastable *** newly formed HCP phase interacts with hydrogen to form a face-centered cubic hydride verified by electron energy loss *** work provides a primary exploration of the formation of compositionally complex metal hydrides in the metastable RHEAs,which are potential candidates for future hydrogen storage material design.

关键词： Refractory high entropy alloy Compositionally complex hydrides Electrochemical polishing Phase transformation Scanning transmission electron microscopy(STEM)/electron energy loss spectroscopy(EELS)

Crystal plasticity model to predict fatigue crack nucleation based on the phase transformation theory

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Acta Mechanica Sinica 2019年第5期35卷 1033-1043页

作者： Lu Liu Jundong Wang Tao Zeng Yao Yao School of Mechanics Civil Engineering and ArchitectureNorthwestern PolytechnicalUniversityXi'an 710072China max-planck-institut für Eisenforschung GmbH Max Planck Str.140237 DüsseldorfGermany

A crystal plasticity model is developed to predict the fatigue crack nucleation of polycrystalline materials,in which the accumulated dislocation dipoles are considered to be the origin of *** describe the overall softening behavior under cyclic loading,a slip system-level dislocation density-related damage model is proposed and implemented in the finite element analysis with Voronoi *** numerical model is applied to calibrate the stress-strain relationship at different cycles before fatigue crack *** parameters determined from the numerical analysis are substituted into a modified phase transformation model to predict the critical fatigue crack nucleation *** with the experimental results of Sn-3.0Ag-0.5Cu(SAC305)alloy and P91 steel,the proposed method can describe the constitutive behavior and predict the fatigue crack nucleation accurately.

关键词： Fatigue crack nucleation Damage Crystal plasticity Finite element Dislocation density

Teaching solid mechanics to artificial intelligence—a fast solver for heterogeneous materials

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npj Computational Materials 2021年第1期7卷 899-908页

作者： Jaber Rezaei Mianroodi Nima H.Siboni Dierk Raabe Microstructure Physics and Alloy Design Max-Planck-Institut für EisenforschungDüsseldorfGermany DeepMetis BerlinGermany

We propose a deep neural network(DNN)as a fast surrogate model for local stress calculations in inhomogeneous non-linear *** show that the DNN predicts the local stresses with 3.8%mean absolute percentage error(MAPE)for the case of heterogeneous elastic media and a mechanical contrast of up to factor of 1.5 among neighboring domains,while performing 103 times faster than spectral *** DNN model proves suited for reproducing the stress distribution in geometries different from those used for *** the case of elasto-plastic materials with up to 4 times mechanical contrast in yield stress among adjacent regions,the trained model simulates the micromechanics with a MAPE of 6.4%in one single forward evaluation of the network,without any *** results reveal an efficient approach to solve non-linear mechanical problems,with an acceleration up to a factor of 8300 for elastic-plastic materials compared to typical solvers.

关键词： artificial network faster

Ab initio energetic study of oxide ceramics with rare-earth elements

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Rare Metals 2006年第5期25卷 549-555页

作者： Matvei Zinkevich Fritz Aldinger max-planck-institut für Metallforschung Institut für Nichtmetallische Anorganische MaterialienUniversitt StuttgartHeisenbergstrasse 3D-70569 StuttgartGermany

Ab initio energetic calculations based on the density functional theory （DFF） and the projector augmented wave method （PAW） for determining the polymorphisms of lanthanide sesquioxides Ln2O3 （where Ln = rare-earth element, Y, and Sc）, LnMO3 perovskites （where M = AI and Ga）, and Ln2B207 pyrochlores （where B = Ti, Zr, and Hf） were reported. The relative lattice stabilities agreed well with the critically assessed results or the experimental results except the C-type Ln2O3 with a cubic structure, for which the calculated total energies were considerably more negative. With the increase of the Ln^3＋-cation radius, the polymorphic structures showed a degenerative tendency. The tendencies and quantities of the enthalpies of formation of the ternary oxide ceramics synthesized from their constituent binary oxides reasonably agreed with the available experimental results, and valuable thermodynamic properties were afforded to the compound, for which no experimental data is available. The enthalpies of formation of both perovskites and pyrochlores tend to become more negative with the increase of the Ln^3＋-cation radius.

关键词： rare earth oxide ceramics ab initio calculation lattice stability enthalpy of formation